1. Technical Field
The present application relates to a technique for using a buffer more efficiently in a router which transfers data to be transmitted and received between a bus master and a slave in a semiconductor integrated circuit including a networked semiconductor bus.
2. Description of the Related Art
In developing an integrated circuit, some people attempt to advance their development more efficiently by recycling and merging together a number of existent bus masters in order to realize the intended function and performance. To make such a development, various kinds of bus masters with mutually different bus widths, bus protocols and required qualities need to be connected together easily.
As a method for getting various kinds of bus masters connected together easily, people have developed a technique which uses a Network on Chip (which will be referred to herein as an “NoC”) to connect a plurality of bus masters through a network of buses. In an NoC, data to be transmitted and received by bus masters which use mutually different bus widths and bus protocols is transformed into packets. And each of those packets is delivered to its destination node via a router by the packet exchange method.
According to the packet exchange method, various kinds of data are packetized into packets, which are then transmitted. As a result, those data can be transferred through the same transmission route. However, if the space left in the buffer of the router that should store those packets ran short during the transfer, then the performance of the transmission route would deteriorate, which is a problem.
Not only an NoC but also a transmission route that adopts the packet exchange method should use such a limited buffer space as efficiently as possible without causing a decline in transmission performance.
Japanese Laid-Open Patent Publication No. 2002-290455 (herein referred to as “the JP Patent Publication”) discloses an exemplary method for using a buffer of the router more efficiently. Nevertheless, the JP Patent Publication relates to a general network technology which uses IP (Internet Protocol) packets. According to the JP Patent Publication, if a buffer of the router is congested, packets in a class with a low priority level are discarded so that packets in a class with a high priority level can use the buffer preferentially. In this manner, a router's limited buffer space can be used more efficiently.